The invention herein described was made in the course of or under a contract or a subcontract thereunder with the United States Department of the Air Force.
This invention relates to gas turbine engines and, more particularly, to combustion chambers for use therein.
Gas turbine engine efficiency is a function of various parameters, among them the temperature achievable within combustion chambers, as well as the amount of air which must be diverted to cool various elements of the engine. Contemporaneously, the structural integrity of an engine is improved if structural loads are carried by elements of the engine which elements are not also subjected to high temperatures and attendant thermal stresses.
In an attempt to raise achievable temperatures within combustion chambers, various materials and alloys have been proposed for use in the construction of the chambers. Two materials which exhibit particularly beneficial resistance to thermal effects are oxide dispersion strengthened materials and various ceramics. Another beneficial material involves a high temperature coating of columbium. A major drawback with respect to the former materials and certain others, however, is that they are difficult or impractical to weld. The inventions disclosed within individuals of the cited patent applications make possible the use of such materials in the construction of combustion chambers. The present invention is particularly adapted to the use of columbium coatings in combustion chambers; however, the concepts hereof are broadly applicable.
The effective application of such high temperature materials as those discussed, in addition to enabling higher temperatures to be reached, also allows a reduction in the amount of cooling fluid required to be directed to the combustion chamber during operation. This reduction enables the engine to operate with increased efficiency.
Structural failures in gas turbine engines in the past have sometimes resulted from the subjection of structural load bearing portions of the engine to thermal stresses associated with high temperatures of combustion. The formation of a combustion chamber in a way which requires the combustion chamber (which is directly exposed to the heat of combustion) to carry structural loads associated with the liner has sometimes resulted in such failures. Use of the configuration of the present invention overcomes these problems by isolating the liner of the chamber from the structural loads associated with the frame encircling the chamber.
Another significant facet of the present invention is that it permits the easy removal of individual liner rings without the necessity of total disassembly of the structural frame and associated components. This, in turn, permits the substitution of new rings for those which may have become worn over extended use, or the repair of individual liner rings which retain a useful life. Such a capability proves a great cost saving with respect to prior art devices wherein combustion chambers have been formed of a substantially unitized construction and wherein damage or wear to a single portion of the chamber has necessitated replacement of large sections or the entirety thereof.